Certain prior art welding systems use bridge topologies in a welding power source to provide AC welding capability. A full bridge topology may be used with just about any power source topology, providing flexibility and the potential to be added to existing designed power sources. The full bridge topology allows easy implementation of zero cross assisting circuits. A blocking diode may be used to protect the devices in the power source from high voltage transients that occur during the zero cross. For certain welding processes such as, for example, an AC gas tungsten arc welding process (GTAW or TIG) or an AC gas metal arc welding process (GMAW or MIG), it is desirable for the arc between the electrode and the workpiece to quickly re-ignite in the opposite polarity direction when the welding current crosses zero.
A welding power source may have a maximum voltage level (e.g., 100 VDC) that it is designed to output. When an AC welding current crosses zero (i.e., changes polarity), the arc extinguishes and may not re-establish. In TIG welding (where there is no wire electrode), if the arc extinguishes, the welding power source may have to repeat the entire arc-establishment process before welding can continue, resulting in an inefficient welding process.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such systems and methods with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings.